this is "world news." tonight, on the trail of a bomber. the new clues. metal fragments from a pressure cooker like this, at the heart of an investigation. video of multiple angles of the key moments revealing exactly what the bomb did. we show you where the bomb went off, and the force of the impact. and tonight the new casualties, including an 8-year-old boy, and a beloved daughter. and we bring you the stories behind those moments we all watched together on tape. a flag at half staff at the white house, a nation on edge, and the world sending messages of support, as the people of boston speak out tonight. our abc news team standing by to bring you the latest, as this special one-hour edition of "world news" begins.

good evening. as we come on the air, this is a country in search of a bomber and there are new clues inside those bombs. at this hour, investigators think one or both of the bombs may have been encased in an ordinary metal pressure cooker. it may have been packed with nailed and ball bearings to inflict more injury. and tonight new details are surfacing about those who died, including the 8-year-old member of the little league. while at the white house, the flag flies at half staff, the president has just announced he will head to boston on thursday and our team is standing by to bring you the latest. the latest reporting and we'll start with abc's brian ross who is no boston tonight. brian? >> reporter: no one is in

custody, but there are new developments about the bomb and the bomber. vffingsors at the crime scene have already recovered the remains of one pressure cooker bomb which failed to fully explode. according to officials briefed on the case. late today the fbi said it's looking for a man carrying an unusually heavy black bag. >> the bag would have been heavy because of the components believed to be in it. >> reporter: the fbi has losts of clues already. the white smoke indicates a bomb built with low velocity mixture turs, not military grade. >> they may not have had the resources as we've seen in other bomb attacks, but they knew how to make the bomb go boom. >> reporter: experts say the large pieces of metal, as seen here in the air suggest the bombs might have been concealed in or under a mailbox or trash barrel, as one witness

described. >> i literally saw the garbage barrel explode. i saw at the flash, the fire, the smoke and i ran as fast as i could. >> all the evidence they collected might not look like much, but the investigators, every small piece of evidence they collect will be a treasure trove. >> reporter: in the fbi belief about the pressure cooker bears out, it will be no surprise to counterterrorism officials who have warned about their possible use for years. there are numerous descriptions online about how to build a pressure cooker bomb, including this detailed one posted in an al qaeda internet publication. april is also a month with significance for domestic terror groups. the month of the waco raid and the oklahoma city bombing. as president obama made clear today, there's still no evidence of who is responsible for this act of terrorism. >> this was a heinous and cowardly act, and given what we now know about what took place, the fbi is investigating it as an act of terrorism.

>> reporter: the fbi agents tell us they have tons of video and somewhere in there will be a picture of the person who planted these two bombs, diane. >> speaking of pictures, i want to ask you about a photo that everybody was e-mailing today. it is a man standing up on top of a roof. you can move in there, you see it right there. what do you know about it? >> reporter: well, it's very intriguing, but authorities say they're giving it no special priority. it's one of many tips and leads they're following. they're really focusing on the person who had that unusually heavy black bag the day of theerates. >> as you said the strongest clues are in the nature of the bomb. up next, abc's jim avila shows us just how far the blast from the bombs traveled. >> reporter: the killer bombs likely contained less than two pounds of common black powder explosive, says one of the nations leading ied experts. even leaving the characteristic white smoke.

bombs designed to spread terror and death with a lethal blast of metal shrapnel. >> looks like he was out to kill and maim. >> hold it right there. here we see windows blown out here, but the buildings themselves are intact. what does that tell us about what this bomber wanted to do? >> that he did not want to take down the building. that wasn't his main target. it was to disrupt the marathon and kill people in that immediate area. >> reporter: houston says this is classic ied design, the kill zone from the blast, one to two yards. according to the accounts from the bomb's site, powerful enough to knock a runner off his feet ten yards away. and topple another man on his couch from the third floor of the building next door, 20 yards away. >> however, the placement is pretty sophisticated. >> reporter: the pressure cooker is well known by the military as

a lethal bomb carrier, covered in training manuals and explained in action in video. >> reporter: they're small, easily made, even crude. but the planning and execution tell us that the terrorist was well trained. >> i would be surprised if it's a lone actor. he's definitely been working on this for a while, the planning and working on putting the devices together. >> reporter: but none of the clues so far tell our expert whether this terrorist was part of any one organization. diane? >> thanks so much, jim. that takes us to abc's martha radda raddatz. been on the phone with sources today. just back from boston. so presumably they're looking at surveillance tapes in this area. what do you know about that? >> you heard brian say there's tons of video. they have surveillance everywhere in that area. it was the boston marathon. of course they had a lot of cameras out there. and you have social media, cellphone video. that's why they're asking for

all this. the hard part here, though, is the more you have, the longer it takes to go through it. the more people you need to go through it. the more experts you need. and meanwhile, this bomber, this terrorist or terrorists are trying to get away. >> and other sense about how long this investigation could be going on and on? >> investigations in the past have had break. in the oklahoma city bombing they made a mistake and got caught in 90 minutes. the world trade center bombing, in 1993, they made a mistake, they caught those people very, very quickly. this one we're way beyond 24 hours and time is really critical in order to get someone. they may solve this crime, but someone may be getting away right now. >> okay, thank you, martha. and there's one more thing we think we know about this bomber. he may have studied last year's race to pinr pinpoint the moment of maximum runners crossing the finish line. the maximum crowd, four hours and 18 minutes in, that's almost

exactly the time his bombs exploded. and from boston tonight, new images, half-eaten sandwiches abandoned on the street where the bombs went off. as dan harris gives us new insight taking us behind those images we all watched together as it happened. >> reporter: tonight new video is giving us fresh, frightening insight into the attacks. look at this cellphone footage, shot by a sectator standing between the two bombs. after the first explosion, there's confusion, but relative calm as people move away. but then after 11 seconds go by -- after the second explosion, panic. in the aftermath, you can see people running alongside walks carpeted in glass -- and victims. >> are you okay?

>> i have a victim here with shrapnel in the leg. >> reporter: police scanner trafics takes us further inside those moments. >> get another ambulance down here at 755 boylston. >> they are on the way, sir, they are on the way. >> reporter: so many images, the face of nicole gross, one of three members of the same family injured. and that 78-year-old runner who was knocked down but picked himself up and finished the race. today boston was crawling with armored vehicles, uniformed national guardsmen and officers armed with high powered rifles. on a normal tuesday afternoon, this part of town would be crawling with foot and road traffic, but today it's on lockdown. police have set up a massive crime scene. take a look at the map. we are on just one corner of what is a 12-block crime scene right in the heart of this city. also today we got our first

details of those who did not survive. 8-year-old martin richard. and 29-year-old krystle campbell. >> i can't believe this has happened. >> reporter: her mother said that her death was just a waste. late today we learned that the third victim was a graduate student at boston university. we do not have a name there. and of course scores of other people were injured in this attack. the current total stand at 176. diane, to give you a sense of how boston is coming together in the wake of these attacks, late today, the red cross announced that it is now turning away blood donors. they say they are simply at capacity. >> all right, thank you, dan. and thinking of everyone in boston today, president obama had a message for the bombers and the world. listen. >> the american people refuse to be terrorized. because what the world saw yesterday in the aftermath of the explosions were stories of

heroism and kindness and generosity and love. so if you want to know who we are, what america is, how we respond to evil, that's it. self-lessly, compassionately, unafraid. >> and we have more new images from this day in boston. families opening their homes to stranded marathoners. a young boy collecting his thoughts in a church near the bombings, and a lone athlete defiantly running along the shores of the charles river early this morning. still ahead right here on "world news," the 8-year-old member of the little league and the town that is rallying around his family tonight. as your life and career change, fidelity is there for your personal economy, helping you readjust your retirement plan along the way. rethink how you're invested. and refocus as your career moves forward.

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they're taking extra security precautions just in case. >> just to be clear, do we have any information about anyone could have come in contact with it? it can be extremely lethal. >> generally it needs to be ingested or inhaled to be dangerous to a person. we have no information that anyone pz been harmed so far, diane. >> i know homeland security is on top of it, as you are, pierre. we'll be back with you soon as you have more information to bring us tonight. so we'll take a break and be back with more breaking news tonight on "world news." back in a moment. w that feels. copd includes emphysema and chronic bronchitis. spiriva is a once-daily inhaled copd maintenance treatment that helps open my obstructed airways for a full 24 hours. you know, spiriva helps me breathe easier. spiriva handihaler tiotropium bromide inhalation powder does not replace fast-acting inhalers for sudden symptoms.

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for a body in motion. and back to the news out of boston. all day today people sharing pictures of a little boy named martin richard. an 8-year-old who was killed in the bomb blast yesterday. his mother and younger sister were hurt too. abc's linsey davis traveled to their hometown. >> reporter: the big, brown smiling eyes of martin richard make the sorrow of what happened monday afternoon all the more palpable. the 8-year-old was known as a little league star. >> he was the fastest kid, just a marvel to watch >> reporter: friends say the family went to the boston marathon every year. but that first explosion ended martin's short life, sending his mother to the hospital with a serious head injury, his younger sister lost a leg. neighbors in this close knit

community are now grieving along with martin's father. >> i was outside with my dog. i saw him get out of the car. he was dressed in hospital scrubs and i said, oh, my god, bill, are you okay? and he didn't even answer me. >> reporter: an outpouring of support and prayers for this family. in a statement, they say,y we thank our family and friends, those we know and those we have never met, for their thoughts and prayers. >> when we would see them, they would all be together, whether it was at church, going to school, on the sports field, they were a very active family, pillars of the community. >> reporter: this community now reeling. its compassion etched in chalk on the drive of the family home. flowers await their return. the town's clock, frozen to mark that moment and the flag at half staff outside martin's school where teachers tonight describe him as an energetic young boy

who had big dreams and high hopes for his future. a vigil is taking place tonight at the richards' family church. an outpouring of prayers for martin's mother and sister who remain in the hospital. >> in boston for us again tonight, linsey davis and amid the grief of those who were lost, there were so many people who inspired us. earlier today i talked to trauma surgeon dr. davide king, who saved lives in iraq and afghanistan. yesterday ran the marathon and then did it again. >> reporter: you completed the marathon? >> that's correct. i was in the athlete's recovery area for about 30-45 minutes. but essentially just left there when the bomb went off and of course immediately came to the hospital. >> reporter: what did you say to yourself when you first heard about this? >> the moment i walked into the emergency room and looked at the

casualties, without even examining the patients in detail, i could just see the pattern of injury and i thought to myself, "this is exactly like i was back in iraq or afghanistan." >> you're finding metallic particles, small metal balls, nails, screws in these wounds? >> that's right. we're not exactly sure what they are. whether they're bb's or metal ball bearings. we're also finding nails and screws and other pieces of metal. they're twisted and deformed. it's not clear whether they're from the bomb itself or the environment around the bomb. >> but the bomb may have hit other metal objects that then splintered apart? >> this is what i'm hearing although i certainly don't know that for a fact. the operations that we have performed are identical to the kind of work we would do in the army at a forward surgical team or combat support hospital. >> well, again, we know there is

heroism, large and small at all times at mass general, and we thank you so much for joining us. i know you've got at least five surgeries today. we'll let you go back to work. >> thank you very much. and coming up next here, a nation on edge. other cities in america, after the tragedy in boston. and chantix helped me quit. i honestly loved smoking, and i honestly didn't think i would ever quit. [ male announcer ] along with support, chantix (varenicline) is proven to help people quit smoking. it reduces the urge to smoke. it put me at ease that you could smoke on the first week. [ male announcer ] some people had changes in behavior, thinking or mood, hostility, agitation, depressed mood and suicidal thoughts or actions while taking or after stopping chantix. if you notice any of these stop taking chantix and call your doctor right away. tell your doctor about any history of depression or other mental health problems, which could get worse while taking chantix. don't take chantix if you've had a serious allergic or skin reaction to it. if you develop these stop taking chantix and see your doctor right away as some can be life-threatening.

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all around the world today people of all nations were sending messages of solidarity to boston. and in this country too, there was new meaning to the injunction, see something, say something. tonight the newest member of our abc news family veteran reporter abc's byron pits is here to tell us about this new normal in american cities tonight. >> reporter: this is america's new normal. the moment terror strikes at home, the nation coils. doft to coast law enforcement, at los angeles's union station, a muscular police presence, and

a measure of anxiety felt lie commuters. >> it puts you on edge. >> we're not safe anywhere. >> it could happen anywhere, even here in california. >> that faith that you have in security of our nation, it's kind of shaken. >> reporter: in downtown seattle, streets were shut down due to a suspicious backpack. the bomb squad sent in its robot, inside a hair dryer. east coast airports had the jitters. at logan airport, delays over suspicious passengers and packages. at new york laguardia, another suspicious item and passengers forced to wait outside in the street. and the comforting sound of resiliencyy. >> i think if i become nervous i'm giving in to something that's going to make me underpowered. >> as citizens, we have to be responsible one to another. >> reporter: meanwhile in

boston, vows unbroken. >> we're strong people and we're not going to let anyone push us around. you mess with one of us, you mess with all of us. >> reporter: all across the country, people sent their best wishes and prayers to boston. we've seen this in america before, when a crisis hits home, this nation will rally. >> so true and byron, it is great to have you with us at abc. and now if you'll allow us tonight, there's a member of our abc family who has died. a man who has been absolutely critical to the kind of reporting we've done today, this week, and so many times before. preston davis, 35 years ago began as an engineer here and rose to become president of broadcast operations and engineering. the first african american president of any division at abc, known, respected, loved by every single person at every level of abc. and tonight we remember preston

davis, who was 63 years old. >> and we thank you for watching the first half of this special one-hour edition of "world news." some of you will be leaving us now, but the others of you, we hope you'll stay with us as we continue with breaking news, the very latest in this special edition of "world news." ♪ [ female announcer ] from more efficient payments. ♪

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